The present invention is related to antennas and, more particularly, is directed towards a conformal microstrip antenna designed in particular to be utilized on a missile or projectile which requires an electrically small construction.
A typical prior art antenna utilized for a telemetry system in a missile consists of a loop antenna comprising a plurality of turns of conducting wire wrapped about the nose section of the missile. A common requirement of such antennas is that they be electrically small, i.e. their maximum dimension be less than a tenth of a wavelength.
Such wire loop antennas characteristically exhibit low gain and an extremely narrow band impedance match. Additionally, the configuration of most of the electrically small antennas of the prior art leads to poor radiation characteristics since, due to their small size, there may be created high current densities, which lead to high I.sup.2 R losses. The electric field of such wire loop antennas is generally polarized transverse to the axis of the missile.
We realized that if the field of the antenna could be polarized axially, currents could be excited along the missile by using the missile body as part of the metallic structure of the antenna to therefore spread out the current density and lower the I.sup.2 R losses, thereby increasing the efficiency of the radiator. In addition to being electrically small, the resultant design had to be compatible with the nose section of the missile, hollow in the center to permit passage of the missile body and/or wires to the telemeter transmitter, and had to be relatively small in diameter and length.
The present invention was advanced with a view towards meeting the above design criteria.